/*
Copyright 2019 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package validation

import (
	"fmt"
	"net"
	"net/url"
	"strings"

	v1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/klog"
	"k8s.io/kops/pkg/apis/kops"
	"k8s.io/kops/pkg/apis/kops/util"
	"k8s.io/kops/pkg/cloudinstances"
	"k8s.io/kops/pkg/dns"
	"k8s.io/kops/upup/pkg/fi/cloudup"
)

// ValidationCluster uses a cluster to validate.
type ValidationCluster struct {
	Failures []*ValidationError `json:"failures,omitempty"`

	Nodes []*ValidationNode `json:"nodes,omitempty"`
}

// ValidationError holds a validation failure
type ValidationError struct {
	Kind    string `json:"type,omitempty"`
	Name    string `json:"name,omitempty"`
	Message string `json:"message,omitempty"`
}

type ClusterValidator interface {
	// Validate validates a k8s cluster
	Validate() (*ValidationCluster, error)
}

type clusterValidatorImpl struct {
	cluster           *kops.Cluster
	instanceGroupList *kops.InstanceGroupList
	k8sClient         kubernetes.Interface
}

func (v *ValidationCluster) addError(failure *ValidationError) {
	v.Failures = append(v.Failures, failure)
}

// ValidationNode represents the validation status for a node
type ValidationNode struct {
	Name     string             `json:"name,omitempty"`
	Zone     string             `json:"zone,omitempty"`
	Role     string             `json:"role,omitempty"`
	Hostname string             `json:"hostname,omitempty"`
	Status   v1.ConditionStatus `json:"status,omitempty"`
}

// hasPlaceHolderIP checks if the API DNS has been updated.
func hasPlaceHolderIP(clusterName string) (bool, error) {

	config, err := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
		clientcmd.NewDefaultClientConfigLoadingRules(),
		&clientcmd.ConfigOverrides{CurrentContext: clusterName}).ClientConfig()
	if err != nil {
		return false, fmt.Errorf("error building configuration: %v", err)
	}

	apiAddr, err := url.Parse(config.Host)
	if err != nil {
		return true, fmt.Errorf("unable to parse Kubernetes cluster API URL: %v", err)
	}
	hostAddrs, err := net.LookupHost(apiAddr.Hostname())
	if err != nil {
		return true, fmt.Errorf("unable to resolve Kubernetes cluster API URL dns: %v", err)
	}

	for _, h := range hostAddrs {
		if h == "203.0.113.123" {
			return true, nil
		}
	}

	return false, nil
}

func NewClusterValidator(cluster *kops.Cluster, instanceGroupList *kops.InstanceGroupList, k8sClient kubernetes.Interface) (ClusterValidator, error) {
	return &clusterValidatorImpl{
		cluster:           cluster,
		instanceGroupList: instanceGroupList,
		k8sClient:         k8sClient,
	}, nil
}

func (v *clusterValidatorImpl) Validate() (*ValidationCluster, error) {
	return validateCluster(v.cluster, v.instanceGroupList, v.k8sClient)
}

// validateCluster validates a k8s cluster with a provided instance group list
func validateCluster(cluster *kops.Cluster, instanceGroupList *kops.InstanceGroupList, k8sClient kubernetes.Interface) (*ValidationCluster, error) {
	clusterName := cluster.Name

	v := &ValidationCluster{}

	// Do not use if we are running gossip
	if !dns.IsGossipHostname(clusterName) {
		contextName := clusterName

		hasPlaceHolderIPAddress, err := hasPlaceHolderIP(contextName)
		if err != nil {
			return nil, err
		}

		if hasPlaceHolderIPAddress {
			message := "Validation Failed\n\n" +
				"The dns-controller Kubernetes deployment has not updated the Kubernetes cluster's API DNS entry to the correct IP address." +
				"  The API DNS IP address is the placeholder address that kops creates: 203.0.113.123." +
				"  Please wait about 5-10 minutes for a master to start, dns-controller to launch, and DNS to propagate." +
				"  The protokube container and dns-controller deployment logs may contain more diagnostic information." +
				"  Etcd and the API DNS entries must be updated for a kops Kubernetes cluster to start."
			v.addError(&ValidationError{
				Kind:    "dns",
				Name:    "apiserver",
				Message: message,
			})
			return v, nil
		}
	}

	var instanceGroups []*kops.InstanceGroup

	for i := range instanceGroupList.Items {
		ig := &instanceGroupList.Items[i]
		instanceGroups = append(instanceGroups, ig)
	}

	if len(instanceGroups) == 0 {
		return nil, fmt.Errorf("no InstanceGroup objects found")
	}

	cloud, err := cloudup.BuildCloud(cluster)
	if err != nil {
		return nil, err
	}

	nodeList, err := k8sClient.CoreV1().Nodes().List(metav1.ListOptions{})
	if err != nil {
		return nil, fmt.Errorf("error listing nodes: %v", err)
	}

	warnUnmatched := false
	cloudGroups, err := cloud.GetCloudGroups(cluster, instanceGroups, warnUnmatched, nodeList.Items)
	if err != nil {
		return nil, err
	}
	v.validateNodes(cloudGroups)

	if err := v.collectComponentFailures(k8sClient); err != nil {
		return nil, fmt.Errorf("cannot get component status for %q: %v", clusterName, err)
	}

	if err = v.collectPodFailures(k8sClient); err != nil {
		return nil, fmt.Errorf("cannot get pod health for %q: %v", clusterName, err)
	}

	return v, nil
}

func (v *ValidationCluster) collectComponentFailures(client kubernetes.Interface) error {
	componentList, err := client.CoreV1().ComponentStatuses().List(metav1.ListOptions{})
	if err != nil {
		return fmt.Errorf("error listing ComponentStatuses: %v", err)
	}

	for _, component := range componentList.Items {
		for _, condition := range component.Conditions {
			if condition.Status != v1.ConditionTrue {
				v.addError(&ValidationError{
					Kind:    "ComponentStatus",
					Name:    component.Name,
					Message: fmt.Sprintf("component %q is unhealthy", component.Name),
				})
			}
		}
	}
	return nil
}

func (v *ValidationCluster) collectPodFailures(client kubernetes.Interface) error {
	pods, err := client.CoreV1().Pods("kube-system").List(metav1.ListOptions{})
	if err != nil {
		return fmt.Errorf("error listing Pods: %v", err)
	}

	for _, pod := range pods.Items {
		if pod.Status.Phase == v1.PodSucceeded {
			continue
		}
		if pod.Status.Phase == v1.PodPending {
			v.addError(&ValidationError{
				Kind:    "Pod",
				Name:    "kube-system/" + pod.Name,
				Message: fmt.Sprintf("kube-system pod %q is pending", pod.Name),
			})
			continue
		}
		var notready []string
		for _, container := range pod.Status.ContainerStatuses {
			if !container.Ready {
				notready = append(notready, container.Name)
			}
		}
		if len(notready) != 0 {
			v.addError(&ValidationError{
				Kind:    "Pod",
				Name:    "kube-system/" + pod.Name,
				Message: fmt.Sprintf("kube-system pod %q is not ready (%s)", pod.Name, strings.Join(notready, ",")),
			})

		}
	}
	return nil
}

func (v *ValidationCluster) validateNodes(cloudGroups map[string]*cloudinstances.CloudInstanceGroup) {
	for _, cloudGroup := range cloudGroups {
		var allMembers []*cloudinstances.CloudInstanceGroupMember
		allMembers = append(allMembers, cloudGroup.Ready...)
		allMembers = append(allMembers, cloudGroup.NeedUpdate...)
		if len(allMembers) < cloudGroup.MinSize {
			v.addError(&ValidationError{
				Kind: "InstanceGroup",
				Name: cloudGroup.InstanceGroup.Name,
				Message: fmt.Sprintf("InstanceGroup %q did not have enough nodes %d vs %d",
					cloudGroup.InstanceGroup.Name,
					len(allMembers),
					cloudGroup.MinSize),
			})
		}

		for _, member := range allMembers {
			node := member.Node

			if node == nil {
				nodeExpectedToJoin := true
				if cloudGroup.InstanceGroup.Spec.Role == kops.InstanceGroupRoleBastion {
					// bastion nodes don't join the cluster
					nodeExpectedToJoin = false
				}

				if nodeExpectedToJoin {
					v.addError(&ValidationError{
						Kind:    "Machine",
						Name:    member.ID,
						Message: fmt.Sprintf("machine %q has not yet joined cluster", member.ID),
					})
				}
				continue
			}

			role := util.GetNodeRole(node)
			if role == "" {
				role = "node"
			}

			n := &ValidationNode{
				Name:     node.Name,
				Zone:     node.ObjectMeta.Labels["failure-domain.beta.kubernetes.io/zone"],
				Hostname: node.ObjectMeta.Labels["kubernetes.io/hostname"],
				Role:     role,
				Status:   getNodeReadyStatus(node),
			}

			ready := isNodeReady(node)

			// TODO: Use instance group role instead...
			if n.Role == "master" {
				if !ready {
					v.addError(&ValidationError{
						Kind:    "Node",
						Name:    node.Name,
						Message: fmt.Sprintf("master %q is not ready", node.Name),
					})
				}

				v.Nodes = append(v.Nodes, n)
			} else if n.Role == "node" {
				if !ready {
					v.addError(&ValidationError{
						Kind:    "Node",
						Name:    node.Name,
						Message: fmt.Sprintf("node %q is not ready", node.Name),
					})
				}

				v.Nodes = append(v.Nodes, n)
			} else {
				klog.Warningf("ignoring node with role %q", n.Role)
			}
		}
	}
}
